Perhaps the UV sterilized the shallow rocky potholes from which I used to drink in Arizona. I vividly recall one into which I plunged my face and drank deeply. Finally satiated, I lifted up and noticed some submerged coyote turds about one foot away. I suffered no harmful effects whatever.
Doesn't necessarily mean you weren't drinking contaminated water. Only that if it was, your system was able to handle it.
And
eeeewwwww!!!